The X-ray Structure of Dtdp-4-keto-6-deoxy-d-glucose-3,4-ketoisomerase.
From: Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706-1544, USA.
The Journal of biological chemistry
- Publish Date: Jun 2007
- ISSN: 0021-9258
- Volume: 282
- Issue: 26
- Pages: 19227-36
- Medium: Print
- Language: English
- Citation (JAMA): Davis Melissa L, Thoden James B, Holden Hazel M, et al. The X-ray Structure of Dtdp-4-keto-6-deoxy-d-glucose-3,4-ketoisomerase.. J. Biol. Chem. Jun 2007;282:19227-36
Abstract
The repeating unit of the glycan chain in the S-layer of the bacterium Aneurinibacillus thermoaerophilus L420-91(T) is composed of four alpha-d-rhamnose molecules and two 3-acetamido-3,6-dideoxy-alpha-d-galactose moieties (abbreviated as Fucp3NAc). Formation of the glycan layer requires nucleotide-activated sugars as the donor molecules. Whereas the enzymes involved in the synthesis of GDP-rhamnose have been well characterized, less is known regarding the structures and enzymatic mechanisms of the enzymes required for the production of dTDP-Fucp3NAc. One of the enzymes involved in the biosynthesis of dTDP-Fucp3NAc is a 3,4-ketoisomerase, hereafter referred to as FdtA. Here we describe the first three-dimensional structure of this sugar isomerase complexed with dTDP and solved to 1.5 A resolution. The FdtA dimer assumes an almost jellyfish-like appearance with the sole alpha-helices representing the tentacles. Formation of the FdtA dimer represents a classical example of domain swapping whereby beta-strands 2 and 3 from one subunit form part of a beta-sheet in the second subunit. The active site architecture of FdtA is characterized by a cluster of three histidine residues, two of which, His(49) and His(51), appear to be strictly conserved in the amino acid sequences deposited to date. Site-directed mutagenesis experiments, enzymatic assays, and x-ray crystallographic analyses suggest that His(49) functions as an active site base.
Mesh Headings (Keywords): Bacillaceae, Bacterial Proteins, Binding Sites, Crystallography, X-Ray, Deoxy Sugars, Dimerization, Isomerases, Protein Structure, Quaternary, Protein Structure, Secondary, Protein Structure, Tertiary, Thymine Nucleotides
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